The principal goals of these studies are to determine how glucocorticoids, growth hormone and thyroid hormones integrate at the cellular level to alter thymus cell metabolism. We will assess the relationship between binding of each hormone to thymocytes and the metabolic effects on carbohydrates and amino acid transport and RNA and protein synthesis. We will determine if glucocorticoid, growth hormone and thyroid hormones act as agonists or antagonists in modulating thymus cell metabolism. Nuclear probes will be used to characterize nuclear subpopulations of glucocorticoid and thyroid hormone receptors, and studies will be undertaken to assess how binding of one hormone affects another. Hormonal responsiveness and binding will be determined in both medullary and glucocorticoid sensitive cortical thymus cells. This research should lead to a clear understanding of how these three hormones integrate in altering thymus cell metabolism. In addition we will observe the mechanism by which these hormones act on thymus cell under conditions which more closely mimic the in vivo situation.